1. Field of the Invention
The present invention relates to transducers, and more particularly to a strain-concentrating, membrane-type transducer.
2. Prior Art
For the measurement of relatively high pressures, it is known in the prior art to use high-pressure transducers that essentially comprise a pressure-sensitive deformable membrane equipped with strain gauges, such as described in patent documents FR-A-2 587 485, FR-A-2 594 224 and FR-A-2 594 546, for instance. The strain gauges affixed to the membrane can be four in number, connected in a bridge configuration.
The membrane can have a more or less complex shape, going from a simple flat membrane to a membrane having a central reinforcement. FIG. 1, for instance, shows a membrane 1 having a peripheral edge section 2 and a central reinforcement 3 so as to define an annular channel 4 in which the strains are contained.
Such a transducer is ill-suited for the measurement of low pressures, e.g. less than 20 bars. Indeed, the membrane, which is normally made of steel, cannot reasonably be less than 0.1 mm thick in the channel portions 4. At such low values, the inevitable thickness dispersions in manufacture give rise to a relatively uncertainty in the transducer's sensitivity, and a correspondingly high error margin in the measurements. Moreover, the membranes tend to be unstable and are prone to inelastic deformations at certain points.
It has also been proposed to measure low pressures using transducers such as illustrated in FIG. 2, where a soft membrane 5 is joined to a beam 6 that detects stresses transmitted by the membrane and on which are affixed a number of strain gauges 7. The membrane is made of thin steel for the maximum flexibility, in order to transmit practically all the stress developed to the beam 6.
The above low-pressure transducers are thus comprised of two fairly complex sub-assemblies, giving rise to inconsistencies in assembly, to the detriment of transducer performance.